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Distributed fibre optic systems allow to get information of the local strain all along the optical fibre. Advanced systems may get strains readings with a spatial resolution of a few mm, and accuracy of a few micro strains. This new technology offer a wide range of possibilities for structural testing, but also for Damage detection, because a crack crossing or growing nearby the optical fiber path will be detected as a local spot with high strains.

Concerning composite laminates, the most feared and common damage are VBID (Barely visible Impact Damage) because they may go undetected to visual inspection, but they cause a drop up to 50% for the compressive strength. These internal delaminations are also accompanied by some local residual strains at the damage area, which are easily detectable if a strain sensor was installed just there. Usually, the laminate edges, like manholes, or the area surrounding doors, are high risk areas for impact damage, so the proposed approach is to bond or embed optical fiber along this perimeter, that may be checked regularly for delaminations. The concept was experimentally demonstrated on laminate edges, and also on internal delaminations, and on stringer run-away. The reliability of the technique has been found to be 100%, always that the damage happened close to the fiber path.